Button?
At the rear of the gun's receiver, there is a rotary axis. A leash is put on the axle, which slides along the trigger rail.
If the trigger rail rises, the trigger shaft turns. Shot-recoil and again and again.

Or do you mean that the gunner is pushing?
He turns the right handle down.

@Fubar2Niner
The submarines and equipment I test under the GWX mod, with 20km atmosphere (M.E.P v5) and the corresponding sensor setting. Everything works perfectly. I think there will not be any special problems in adapting to supermods.

At the rear of the gun's receiver, there is a rotary axis. A leash is put on the axle, which slides along the trigger rail.
If the trigger rail rises, the trigger shaft turns. Shot-recoil and again and again.

Gun Flak C/38 is short barrel recoil operated. The barrel after the shot rolls back to 20-24mm and transmits the impulse to the bolt, the gun recharges. recoil is taken by buffer springs inside the gun cradle. For game, gun and gun cradle are placed in "Barrel" nod.

Trigger mechanism: 20mm flak carriage, have the trigger mechanism is handle-actuated. Right handle for double barrel carriage, left handle for single barrel carriage. It mean, for game we make two animations. Yes it is not convenient, but the animation for a single barrel carriage, absolutely does not fit the double barrel carriage.

Handle of firing turns downwards (1)
Through the hinge, the force is transmitted to the axis (1A)
The axis (1A) is in constant engagement with the rail (2L) and through the hinges with the rail (2R)
The trigger (3), on the back of the gun, is in the form of a small handwheel, the handle of which is raised to fire the gun. Handwheel is constantly in contact with the rail. (2L 2R)
After the shot, the cannon rolls back to a distance of 85mm (normal recoil). (4) If the fire is being fired at the gun's zenith position, the recoil can increase to 125mm (in reality).

Models of propellers corrected, rudders too.

before

After

In Inventor

@ For interested

Some time ago, I collected information about German periscopes. In my field of vision, I found documents on American periscopes T2 and T4. Making models C / 8 and C / 2 in parallel made and American. At present, the models are dead weight and do not benefit the community. If there is a desire and skills, then you can use these models for American submarines.
Models are not optimized, not scaled for the game and without textures.

Sights for anti-aircraft guns are slightly modified. The front sight is adjusted for shooting not only by planes, but also by small ships (boats, yachts, etc.). The rear sight is absolutely useless in the game and redone for accurate shooting at a distance of 3000 meters.
Distances:
Internal ring 2000m (aim at the target)
The aim of the sight is 3000 m (exactly between the sharp corners)
Middle ring 4000m (set on target)